Soil organic carbon accumulation modes between pioneer and old-growth forest ecosystems

1. Increasing evidence suggests that high biomass and litterfall do not necessarily bring about soil organic carbon (SOC) sinks, contrary to the assumption that higher litterfall implies higher SOC when designing carbon models. The underlying mechanism is related to the quality of litter. 2. We conducted 15 years (2000–2015) of consecutive field measurements of δ13C values in SOC and plants in a pioneer forest (Pinus massoniana forest, PF) and an old-growth forest (monsoon evergreen broadleaved forest, BF), using an isotope mixing model based on mass balance to quantify the effects of vegetation on SOC stock and soil characteristics. 3. The carbon to nitrogen (C/N) ratio of litter in BF was lower than that in PF. The proportion of organic carbon yield input to the soil (Cinput) to the total litter carbon loss during decomposition was 38.7 ± 3.3% and 28.0 ± 2.1% in BF and PF, respectively. New carbon input was higher in BF (148.7 ± 8.8 g C m−2 yr−1) than PF (99.7 ± 4.5 g C m−2 yr−1), tho...

1. 越来越多的研究证据表明，高生物量与凋落物输入未必会形成土壤有机碳（soil organic carbon, SOC）汇，这与碳模型构建中"更高的凋落物输入对应更高土壤有机碳储量"的预设相悖，其核心机制与凋落物品质密切相关。2. 本研究于2000年至2015年间，对先锋林（马尾松林，Pinus massoniana forest, PF）与成熟林（季风常绿阔叶林，monsoon evergreen broadleaved forest, BF）的土壤有机碳及植物的δ¹³C值开展了长达15年的连续野外定位观测，并基于质量守恒的同位素混合模型，量化植被对土壤有机碳储量及土壤特性的影响。3. 季风常绿阔叶林凋落物的碳氮比（C/N）低于马尾松林。分解过程中，输入土壤的有机碳产出量占总凋落物碳流失量的比例在BF中为38.7 ± 3.3%，在PF中为28.0 ± 2.1%。BF的新碳输入量为148.7 ± 8.8 g C m⁻² yr⁻¹，高于PF的99.7 ± 4.5 g C m⁻² yr⁻¹，tho...